Beryllium atomic weight

Atomic weights are known most accurately for elements which have only 1 stable isotope the relative atomic mass of this isotope can be determined to at least 1 ppm and there is no possibility of variability in nature. There are 20 such elements Be, F, Na, Al, P, Sc, Mn, Co, As, Y, Nb, Rh, I, Cs, Pr, Tb, Ho, Tm, Au and Bi. (Note that all of these elements except beryllium have odd atomic numbers — why )... 

He also points out several times the important evidential role played by the success of Mendeleev s contrapredictions —the corrections of atomic weight values previously assigned to already known elements—such as beryllium, uranium and tellurium—so that they fitted into his table smoothly. And indeed the most elaborate statement of Brush s general conclusion seems to be the following ... 

Historians differ regarding the precise assignment of elements to these values. In particular they disagree with respect to the identity of the element depicted as 7 or 14. According to some it is twice the atomic weight of lithium, while others maintain that it is beryllium using an older value for its atomic weight. 

Mendeleev arranged the elements into seven groups. Lithium (atomic weight 7) was followed by beryllium (9), boron (11), carbon (12), nitrogen (14), oxygen (16), and fluorine (19). The next element in order of atomic weight was sodium (23), which had properties similar to those of lithium. Therefore, Mendeleev pinned the card for sodium under that for lithium. Six more cards were placed in the second row, ending with chlorine under fluorine. He continued in... 

Prout did not consider himself a proficient experimentalist nonetheless, he designed and carried out experiments to determine the weights of such atoms as iodine, phosphorus, sodium, iron, zinc, potassium, and beryllium. For other elements he accepted the atomic weights that had been measured by scientists he considered trustworthy. Of critical importance was the atomic weight accepted for hydrogen itself and for this Prout used the value measured by Davy. With these data in hand, Prout pro-... 

The most common moderators are substances of low atomic weight such as heavy water (deuterium oxide) or graphite. Hydrides (binary compounds corrtaining hydrogen), hydrocarborrs, and beryllium and beryllium oxide have also been used as moderators in certain specialized kinds of reactors. 

In 1885 the issue was finally conclusively settled in favor of Mendeleev by measurements of the specific heat of beryllium at elevated temperatures. These experiments pointed to an atomic weight of 9.0, in reasonable agreement with Dulong and Petit s law and supported the di-valency of the element (Humpidge, 1885). Above all else, Mendeleev persisted in the belief that beryllium lies in group II because of his faith in the validity of the periodic law, which he believed was essentially a feature of the transcendental elements. All else was rationalized around this central tenet. 

Greenaway, Frank. 1969. "On the Atomic Weight of Glucinium (Beryllium). Second Paper." Chemistry in Britain 5 97-99. 

The members of Division B differ from the alkaline earth metals by being more easily reduced to the metallic state all the elements are stable in the air at ordinary temperatures, except beryllium, which is slowly oxidized in moist air the ease of reaction with steam decreases with increased atomic weight. 

Basic beryllium acetate is prepared by the action of glacial acetic acid upon the dry carbonate or hydroxide. It is only slightly soluble in water but is hydrolyzed, becoming soluble. It melts, boils, and sublimes without decomposition. It was used by Parsons for his atomic weight determinations. 

Mendel eff had no room in his Periodic Table for an element with this atomic weight he had, however, a vacancy for one,of 9 and in his table dated 1869 (p. 170) he placed beryllium between lithium and boron, ascribing to it a valency of two. Confirmation was afforded when in 1884 Nilson and Pettersson determined the vapour density of its chloride, showing its formula to be BeCl2, and again when in 1887 Mallardf observed that crystallised beryllia is isomorphous with crystallised zinc oxide, ZnO, and must therefore have a similar structure, namely BeO. 

The atomic weight of beryllium is very close to <>i. I ln first determination was made by Berzelius (1815 i) early in the last century and were little more than approximations. The corrected results of other investigators with the ratio determined are as follows ... 

Beryllium Sulphate Tetrahydrate, BeS0. 4H20.— The tetrahydrate was first prepared by. Berzelius, (1815 i) who considered it to be an acid salt. Awdejew (1842 2) first determined its true character and used the salt to determine the atomic weight of beryllium. It was also employed for this purpose by Weeren (1854 i), Klatzo (1869 i)> Nilson and Pettersson (1880 6) and Kriiss and Moraht (1890 7). Parsons (1904 5) showed that the sulphate lost water continuously over phosphoric anhydride and discarded it as a means of determining the atomic weight of the element. This salt of beryllium has been studied more than any other compound of the metal. 

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